Energized Fluids Research Articles

Evaluation of matrix energization effect of pre-fracturing method in tight reservoirs- A comparative study of CO2, N2, and water

The exacerbation of the greenhouse effect has created an urgent global demand for large-scale utilization of CO2, making it a significant concern for industries worldwide. During the fracturing process, CO2 possesses unique properties that enable the formation of intricate fracture networks, presenting promising applications. However, the potential of CO2 as a medium for enhancing recovery through fracturing remains largely unexplored. This paper highlights the priority of using CO2 as an energized fluid by comparing the pressure and oil recovery performance with N2 and water. Initially, CO2-oil swelling tests were conducted to assess the impact of CO2 injection on the physical properties of crude oil. Subsequently, the matrix energization performance of the three fracturing fluids was analyzed from two perspectives: pressure augmentation and pressure maintenance. The Online Nuclear Magnetic Resonance (NMR) method is proposed to further evaluate the oil replacement performance of fracturing fluids. The experiment results suggest that nitrogen is more effective in raising reservoir pressure, hydraulic fracturing exhibits superior formation energy maintenance, and CO2 demonstrates favorable performance in both aspects. Meanwhile, CO2 remains capable of recovering the largest amount of oil, with a recovery of up to 10.19%, and the oil recovery for nitrogen and water is 9.39% and 6.37%, respectively. Finally, a field-scale numerical model was developed to evaluate the matrix energization performance and oil recovery efficiency. In contrast to water and nitrogen, CO2 exhibits a heightened capacity for oil recovery. However, this advantage is proved to be constrained when the injection volume of CO2 is limited. CO2 can fully leverage its benefits when a substantial injection volume is employed, and reasonable optimization of CO2 injection amount can maximize the benefits.

A novel methodology for the design of diffuser-augmented hydrokinetic rotors

Shrouded wind and hydrokinetic turbines are being widely studied nowadays. Although actuator disk studies have concluded that the addition of a diffuser around a rotor can improve the Power Coefficient, not many designs have realized those benefits when compared to standard high performance bare turbines, as shown by Nunes et al. (2020) [1]. One reason for low power coefficient on several designs is massive flow separation on the hub surface due to high adverse pressure gradient inside the diffuser, resulting on low mass flow capture and, hence, poor performance. This work presents a novel design methodology for shrouded rotors, which takes into consideration the influence of the entire linear cascade on each annular section. Also, the blade root is left unloaded to guarantee that no boundary layer separation occurs on the hub surface by allowing a layer of energized fluid to bypass the rotor. A turbine modeled by this method has been numerically studied and is shown herein to deliver a peak power coefficient of 0.415 normalized by the diffuser's largest cross sectional area.

Influence of Geometric Variations of an Inlet Cover Bleed System on Inducer Performance for an Axial Pump Operating Under Cavitating Conditions

AbstractA stability control device (SCD) is a passive inlet cover treatment that can be applied to high suction performance inducers. Significant improvements in stability have been observed when an inducer operates with an SCD, including suppression of backflow at the leading edge of the inducer at low off-design flow coefficients. This is possible because of a local increase in mass flow at the leading edge of the pump, which allows an inducer to operate with an incidence near the design point value over a wide range of flow coefficients. In this paper, the suction performance of several inducers was explored with several different SCD geometries and at different flow coefficients. Specifically, five different SCD geometries were considered to explore the influence that SCD bleed slot width and resistance to flow through the SCD channel have on inducer performance. Further, removal of tangential velocity of the energized fluid transporting through the SCD channel was considered for some scenarios to highlight the impact of swirl on inducer performance. The results reveal that for all inducers and SCD combinations considered, the most important factor affecting the mass flow through the SCD, and subsequent mass flow gain, is the inlet diffusion of the inducer. This holds for both single-phase and multiphase scenarios. Further, the cavitation number where cavitation first starts to develop in the blade throat passage of the inducer is primarily dependent on the inlet blade angle and not the SCD geometry. Consequently, the shape of the cavitation breakdown curve is largely determined by the inducer blade angle.

Evaluation of EOR potential of energized fluid fracturing – From an energy perspective

Energized fluid fracturing utilizes the high compressibility of fluids and their compatibility with the formation. After the fracturing, the energy stored in these fluids helps to facilitate flow back and to drive oil and gas out. Some papers and patents propose the ideas but with few field tests. Some papers predict the enhanced oil recovery (EOR) potential assuming a fracture network is enhanced from CO2 fracturing. No quantitative analysis has been performed to analyze the EOR potential from an energy perspective in the literature. In this paper, a field test of CO2 fracturing was analyzed to discuss the EOR potential. The test data are used to calibrate a simulation model to quantitatively analyze the potential to improve or enhance oil recovery. The EOR potential of energized fracturing fluids is discussed. It is observed that the volume from the CO2 injection for fracturing is very limited so that the potential to enhance oil recovery is not significant. Such CO2 fracturing process is analog to one cycle of huff-n-puff CO2 injection for the EOR purpose after fracturing. If the injection time or injection volume during one cycle of huff-n-puff injection is like that for a typical fracturing process, the EOR potential from such one cycle huff-n-puff injection is very limited. Therefore, it can be derived that the EOR potential from energized fracturing fluids is limited.

Experimental Investigation on Enhanced-Oil-Recovery Mechanisms of Using Supercritical Carbon Dioxide as Prefracturing Energized Fluid in Tight Oil Reservoir

SummaryFracturing is the necessary means of tight oil development, and the most common fracturing fluid is slickwater. However, the Loess Plateau of the Ordos Basin in China is seriously short of water resources. Therefore, the tight oil development in this area by hydraulic fracturing is extremely costly and environmentally unfriendly. In this paper, a new method using supercritical carbon dioxide (CO2) (ScCO2) as the prefracturing energized fluid is applied in hydraulic fracturing. This method can give full play to the dual advantages of ScCO2 characteristics and mixed-water fracturing technology while saving water resources at the same time. On the other hand, this method can reduce reservoir damage, change rock microstructure, and significantly increase oil production, which is a development method with broad application potential.In this work, the main mechanism, the system-energy enhancement, and flowback efficiency of ScCO2 as the prefracturing energized fluid were investigated. First, the microscopic mechanism of ScCO2 was studied, and the effects of ScCO2 on pores and rock minerals were analyzed by nuclear-magnetic-resonance (NMR) test, X-ray-diffraction (XRD) analysis, and scanning-electron-microscope (SEM) experiments. Second, the high-pressure chamber-reaction experiment was conducted to study the interaction mechanism between ScCO2 and live oil under formation conditions, and quantitively describe the change of high-pressure physical properties of live oil after ScCO2 injection. Then, the numerical-simulation method was applied to analyze the distribution and existence state of ScCO2, as well as the changes of live-oil density, viscosity, and composition in different stages during the full-cycle fracturing process. Finally, four injection modes of ScCO2-injection core-laboratory experiments were designed to compare the performance of ScCO2 and slickwater in terms of energy enhancement and flowback efficiency, then optimize the optimal CO2-injection mode and the optimal injection amount of CO2 slug.The results show that ScCO2 can dissolve calcite and clay minerals (illite and chlorite) to generate pores with sizes in the range of 0.1 to 10 µm, which is the main reason for the porosity and permeability increases. Besides, the generated secondary clay minerals and dispersion of previously cemented rock particles will block the pores. ScCO2 injection increases the saturation pressure, expansion coefficient, volume coefficient, density, and compressibility of crude oil, which are the main mechanisms of energy increase and oil-production enhancement. After analyzing the four different injection-mode tests, the optimal one is to first inject CO2 and then inject slickwater. The CO2 slug has the optimal value, which is 0.5 pore volume (PV) in this paper.In this paper, the main mechanisms of using ScCO2 as the prefracturing energized fluid are illuminated. Experimental studies have proved the pressure increase, production enhancement, and flowback potential of CO2 prefracturing. The application of this method is of great significance to the protection of water resources and the improvement of the fracturing effect.

Improving hydraulic fracturing effectiveness in depleted and low-pressure reservoirs using N2-energized fluids

Foamed and energized fluids fracturing has been used in both conventional and unconventional reservoirs, as they reduce the amount of water used and hence minimize deleterious impact on water-sensitive formations. They also aid in the flow back after treatment in reservoirs where drawdown is limited. In this paper, the most important foam properties are presented, in addition, when to use energized fluids fracturing and how to choose the best energizing component with the best quality. The impact of N2-energized fluids fracturing (NEF) on wells that were previously fractured using conventional fracturing fluids is also presented. In addition, a comparison between the results of N2-energized fluids fractured and conventional fluid fractured wells is presented. The effect of using 20 to 50% (NEF) on production through surface well testing and live production data showed excellent and sustainable production rates. An economical study is presented through comparing the total capital cost of both NEF and conventional fluids fracturing, in addition to the hydrocarbon recovery of wells after both types. Data considered in this work represent about 40 wells fractured using NEF in the Egyptian Western Desert.

(Invited) Understanding Benzothiadiazole Based Anolyte Materials for Nonaqueous Redox Flow Cells

Redox-active organic materials (ROMs) have shown great promise for redox flow battery applications but generally encounter limited cycling efficiency and stability at relevant redox material concentrations in nonaqueous systems. In this talk, a new family of heterocyclic organic anolyte molecules, 2,1,3-benzothiadiazole (BZNSN) and derivatives,1-2 will be discussed, which demonstrated high solubility, low redox potential, and fast electrochemical kinetics. By coupling BZNSN with a benchmark catholyte ROM (DBMMB), the nonaqueous organic flow battery delivered significant improvement in cyclable redox material concentrations and cell efficiencies compared to the state-of-the-art nonaqueous systems. In order to obtain an insightful understanding of this family of molecules, a series of derivatives have been developed by varying the 5-position substitutions with tunable electronic accepting/withdrawing features. The substituent effects on their properties of interest have been examined, including redox potentials, calendar lives of charged ROMs in an electrolyte, and the flow cell cycling performance. While the calendar life of energized fluids can be tuned in a predictable fashion over a wide range, the improvements in the calendar life do not directly translate into the enhanced cycling performance. This finding strongly indicates the significant role of structural engineering in achieving improvement of radical ion stability, suggesting a generic guidance for developing long-cycling ROM-based flow cells. Figure 1 Structures and cyclic voltammogram of benzothiadiazole derivatives and the correlation of the half-decay lifetime of the radical anions with the redox potentials. Mind the logarithmic vertical scale. Duan, W.; Huang, J.; Kowalski, J. A.; Shkrob, I. A.; Vijayakumar, M.; Walter, E.; Pan, B.; Yang, Z.; Milshtein, J. D.; Li, B.; Liao, C.; Zhang, Z.; Wang, W.; Liu, J.; Moore, J. S.; Brushett, F. R.; Zhang, L.; Wei, X.,. ACS Energy Letters 2017, 2(5), 1156-1161. 2. Huang, J.; Duan, W.; Zhang, J.; Shkrob, I. A.; Assary, R. S.; Pan, B.; Liao, C.; Zhang, Z.; Wei, X.; Zhang, L..Journal of Materials Chemistry A 2018, 6 (15), 6251-6254. Figure 1

A Unified Model To Predict Flowing Pressure and Temperature Distributions in Horizontal Wellbores for Different Energized Fracturing Fluids

Summary Energized fracturing fluids, including foams, carbon dioxide (CO2), and nitrogen (N2), are widely used for multistage fracturing in horizontal wells. However, because density, rheology, and thermal properties are sensitive to temperature and pressure, it is important to understand the flow and thermal behaviors of energized fracturing fluids along the wellbore. In this study, a unified steady-state model is developed to simulate the flow and thermal behaviors of different energized fracturing fluids and to investigate the changes of fluid properties from the wellhead to the toe of the horizontal wellbore. The velocity and pressure are calculated using continuity and momentum equations. Temperature profiles of the whole wellbore/formation system are obtained by simultaneously solving energy equations of different thermal regions. Temperature, pressure, and energized-fluid properties are coupled in both depth and radial directions using an iteration scheme. This model is verified against field data from energized-fluid-injection operations. The relative average errors for pressure and temperature are less than 5%. The effects of injection pressure, mass-flow rate, annulus-fluid type, foam quality, and proppant volumetric concentration on pressure and temperature distributions are analyzed. Influence degrees of these operating parameters on the bottomhole pressure (BHP) for different energized fracturing fluids are calculated. The required injection parameters at the surface to achieve designed bottomhole treating parameters for different energized fracturing fluids are compared. The results of this study might help field operators to select the most-suitable energized fluid and further optimize energized-fluid-fracturing treatments.

Thiadiazoles As Anolytes for Nonaqueous Redox Flow Cells

Understanding structure-property relations is essential for designing energy-rich redox active materials (ROMs) for all-organic redox flow batteries.1-2 Herein we examine thiadiazole ROMs for storage of negative charge in the flow cells.3 These versatile molecules have excellent solubility and low redox potentials, allowing to achieve high energy density. By systematically incorporating groups with varying electron accepting/withdrawing ability, we have examined substituent effects on their properties of interest, including redox potentials, calendar lives of charged ROMs in electrolyte, and the flow cell cycling performance. While the calendar life of energized fluids can be tuned in a predictable fashion over a wide range, the improvements in the calendar life do not automatically translate into the enhanced cycling performance, indicating that in addition to the slow reactions of charges species in the solvent bulk, there are other parasitic reactions that occur only during electrochemical cycling of the cell and can dramatically affect the cycling lifetime. This finding strongly indicates the significant role of structural engineering in achieving improvement of radical ion stability, suggesting a generic guidance for developing long-cycling ROM-based flow cells. With these molecules we are on the very edge of possibility, reaching the compromise between the highest energy density and the stability of the radical anion that can be achieved in acetonitrile. We believe that setting these limits is more important for the energy storage community than surveying of different classes of the anolytes. Figure 1 Structures and cyclic voltammogram of benzothiadiazole derivatives and the correlation of the half-decay lifetime of the radical anions with the redox potentials. Mind the logarithmic vertical scale. Zhang, J.; Yang, Z.; Shkrob, I. A.; Assary, R. S.; Tung, S. o.; Silcox, B.; Duan, W.; Zhang, J.; Su, C. C.; Hu, B.; Pan, B.; Liao, C.; Zhang, Z.; Wang, W.; Curtiss, L. A.; Thompson, L. T.; Wei, X.; Zhang, L., Annulated Dialkoxybenzenes as Catholyte Materials for Non-aqueous Redox Flow Batteries: Achieving High Chemical Stability through Bicyclic Substitution. Advanced Energy Materials 2017, 7 (21), 1701272-n/a.Zhang, L.; Zhang, Z.; Redfern, P. C.; Curtiss, L. A.; Amine, K., Molecular engineering towards safer lithium-ion batteries: a highly stable and compatible redox shuttle for overcharge protection. Energy & Environmental Science 2012, 5 (8), 8204-8207.Duan, W.; Huang, J.; Kowalski, J. A.; Shkrob, I. A.; Vijayakumar, M.; Walter, E.; Pan, B.; Yang, Z.; Milshtein, J. D.; Li, B.; Liao, C.; Zhang, Z.; Wang, W.; Liu, J.; Moore, J. S.; Brushett, F. R.; Zhang, L.; Wei, X., “Wine-Dark Sea” in an Organic Flow Battery: Storing Negative Charge in 2,1,3-Benzothiadiazole Radicals Leads to Improved Cyclability. ACS Energy Letters 2017, 2 (5), 1156-1161. Figure 1

Projekt badawczy: ”Projektowanie, wpływ na środowisko i skuteczność działania energetyzowanych cieczy do szczelinowania skał zbiornikowych ropy i gazu Europy Środkowej” (ENFLUID) – założenia, przebieg i rezultaty

Projekt badawczy: ”Projektowanie, wpływ na środowisko i skuteczność działania energetyzowanych cieczy do szczelinowania skał zbiornikowych ropy i gazu Europy Środkowej” (ENFLUID) – założenia, przebieg i rezultaty

Toward Improved Catholyte Materials for Redox Flow Batteries: What Controls Chemical Stability of Persistent Radical Cations?

Catholyte materials are used to store positive charge in energized fluids circulating through redox flow batteries (RFBs) for electric grid and vehicle applications. Energy-rich radical cations (RCs) are being considered for use as catholyte materials, but to be practically relevant, these RCs (that are typically unstable, reactive species) need to have long lifetimes in liquid electrolytes under the ambient conditions. Only few families of such energetic RCs possess stabilities that are suitable for their use in RFBs; currently, the derivatives of 1,4-dialkoxybenzene look the most promising. In this study, we examine factors that define the chemical and electrochemical stabilities for RCs in this family. To this end, we used rigid bis-annulated molecules that by design avoid the two main degradation pathways for such RCs, viz., their deprotonation and radical addition. The decay of the resulting RCs are due to the single remaining reaction: O-dealkylation. We establish the mechanism for this reaction and...

Technology Focus: Well Testing (February 2015)

Technology Focus With the success of hydraulic fracturing in the US shale-gas plays, why are more operating companies not using energized fluids to minimize the use of water, decrease the amount of proppant required, and (theoretically) enhance long-term productivity? It appears that Canadians have been somewhat more receptive to the idea and are more willing to use energized fluids, with apparently positive results. Perhaps it is too early in the game to convince operators in the US to take another look at this technology with an open mind. Allow me to start a dialogue in this area. The perception that using energized fluids is more expensive to achieve the same goal could be one hurdle keeping operators from using them. Nonetheless, let us take a step back and think of some of the more obvious, readily understood benefits: minimizing the use of water and decreasing the amount of proppant. Every operator knows the vast quantities of water required in hydraulic fracturing. This is a commodity that appears to be readily available, but it is not. And this problem will only be exacerbated with time. One of the insidious issues is that not all the water used during fracturing is recovered when flowing back the well, and whatever water is recovered cannot be used in subsequent fracturing stages. Hence, there are huge costs associated with water alone. Proppant, the nice, homogeneous sand grains that keep the fractures open and permeable, is also costly. Decreasing the amount required per stage is equivalent to more money in the operator’s pockets. When one realizes that many countries with enormous shale-gas plays do not have vast resources of readily available water, then the game changes. This may even result in an excellent public relations opportunity when the general public realizes that oil companies care about the environment and the precious resources. For this issue of JPT, it was quite difficult to select three articles because there were so many excellent papers. I have attempted to narrow down the many papers to three that provide a broad perspective and the astute use of well-test data to be insightful to all readers. The interested reader will find many good articles on this subject in the OnePetro library. JPT Recommended additional reading at OnePetro: www.onepetro.org. OTC 25207 Innovative Positioning of Downhole Pressure Gauges Close to Perforations in HP/HT Slim Well During a Drillstem Test by AbdulHakim Al-Nahdi, Saudi Aramco, et al. SPE 171686 Successful DST Methodology Adopted in Highly Deviated Deep, Sour, and HP/HT Exploratory Well: A Case Study by Abdulla Al-Ibrahim, Kuwait Oil Company, et al. IPTC 16427 Mini-DST To Characterize Formation Deliverability in Unconventional Reservoirs by B. Kurtoglu, Marathon, et al.

STEALTH ADAPTED VIRUSES AND THE ALTERNATIVE CELLULAR ENERGY (ACE) PATHWAY IN ALZHEIMER'S DISEASE

STEALTH ADAPTED VIRUSES AND THE ALTERNATIVE CELLULAR ENERGY (ACE) PATHWAY IN ALZHEIMER'S DISEASE

A New 3D Compositional Model for Hydraulic Fracturing With Energized Fluids

Summary While several 3D fracturing models exist for incompressible water-based fluids, none are able to capture the thermal and compositional effects that are important when using energized fluids such as CO2, N2, LPG, and foams. This paper introduces a new 3D, compositional, non-isothermal fracturing model. The new model predicts changes in temperature and fluid density. These changes are treated on a firm theoretical basis by using an energy-balance equation and an equation of state, both in the fracture and in the wellbore. The model is capable of handling any multicomponent mixture of fluids and chemicals. Changes in phase behavior with temperature, pressure, and composition can be modeled. A new simulator has been developed based on the compositional model presented in this paper. The simulator is validated for traditional fluid formulations against known analytical solutions and against a well-established commercial fracturing simulator. Results from the new simulator are then presented for energized fluids such as CO2 and LPG. In particular, the compositional model shows how fluid expansion and viscosity reduction impact fracture growth. These effects are not captured by traditional fracturing simulators. The compositional tool is specifically suited for fracture design in formations in which energized fluids constitute a viable alternative to traditional fracturing fluids.

Fluid Selection for Energized Hydraulic Fractures

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 124361, ’Fluid Selection for Energized Hydraulic Fractures,’ by Kyle E. Friehauf and Mukul M. Sharma, SPE, University of Texas at Austin, prepared for the 2009 SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 4-7 October. Traditional hydraulic-fracture simulators do not take into account the compositional, thermal, and phase-behavior effects that are crucial to the success of energized fractures. Traditional water-based fracturing fluids are not ideally suited for use in tight, depleted, or water-sensitive formations. Gas-energized fracturing fluid addresses the water-trapping problem by creating a high gas saturation in the invaded zone, thereby facilitating gas flowback. A fully compositional fracture simulator was used to evaluate different designs for energized fractures. It showed that energized fluids should be applied to rocks when the drawdown pressure is insufficient to remove the liquid. Use of a compositional fracture simulator allows systematic design of energized-fracture treatments. Introduction A hydraulic-fracturing process becomes energized with the addition of a compressible, sometimes soluble, gas component into the treatment fluid. Energizing the fluid creates a high gas saturation in the invaded zone, thereby facilitating gas flowback. It is estimated that one-third of the fractures pumped in the US are energized by a gaseous phase. Energized-fluid fracturing is common in reservoirs that are water sensitive or that have a low pore pressure or low permeability. In conducting this study, the hydraulic-fracturing model used compositional and energy balances and coupled them with phase behavior, making this model applicable to energized fluids. The productivity-index (PI) -ratio values were calculated with a PI model that takes into account varying fracture conductivity and the damage around the fracture face caused by fluid invasion. Multiphase-Fracturing-Fluid Properties As with all fluids, the properties of an energized fracturing fluid depend on fluid composition and the range of conditions under which the fluid is applied. Commonly, CO2 or N2 are added to a traditional water-based fluid to energize the fluid. This paper focused on these fluid systems because they are used most often and because their rheology has been studied to a great extent, but methanol is another possible component. This paper discusses commonly used fluid systems containing the following component mixtures: CO2/H2O, N2/H2O, and CO2/methanol/H2O.

New Single-Well Standalone Gas Lift Process Facilitates Barnett Shale Fracture-Treatment Flowback

Summary When performing multiple fracture treatments in horizontal Barnett shale wells, many operators choose to use artificial lift to remove fracture fluids rather than incur the expense of energized fluids that may not be effective. Gas lift has been a popular artificial lift method to remove fracture fluids because it allows for high liquid flow rates and is excellent at handling flowback sand. Its disadvantage is that a source of lift gas is required to initiate gas lift, with this source typically being other nearby gas wells or a third-party gas pipeline. In new exploration areas such as the Barnett, often neither is available. Operators resort to costly nitrogen-membrane units to provide lift gas but are left with questions about the net gas produced (since returning nitrogen and produced natural gas are combined downhole then vented to the atmosphere). A new system (patent pending) has been developed that addresses gas lift's issues of initially filling the system with lift gas, as well as maintaining this gas so that additional gas is not required. Being a closed-loop system, it also provides for very accurate measurement of net-gas production by measuring any gas in excess of that needed for lift, and discharging the same to a flare stack. The paper will describe the major components used in this system, present a case history, and address the significant cost reductions and other benefits realized.

Development and Field Application of a Low-pH, Efficient Fracturing Fluid for Tight Gas Fields in the Greater Green River Basin, Wyoming

Summary Hydraulic fracturing has proved to be one of the best technologies to improve productivity from tight gas wells. In such low-permeability reservoirs, careful consideration must be given to fracturing fluid selection. Some reservoirs are underpressured and require the use of energized fluids, while others are sensitive to water-based fluids because of clay swelling and migration. Proppant pack damage because of gel residue is one of the primary causes of low production rates after hydraulic fracturing treatments. To minimize the damage and maximize production, a new premium, highly efficient fracturing fluid was developed. This premium system incorporates low-polymer-loading carboxymethyl guar polymer and a zirconium-based crosslinker. An adjustable crosslink delay makes the fluid ideal for deep-well fracturing and coiled-tubing treatment as frictional pressure losses can be minimized. The system can be energized or foamed with carbon dioxide (CO2) and nitrogen (N2) or may also be used in binary foam systems. This paper will provide details on the new fracturing fluid system, in terms of proppant pack cleanup, rheological properties, and fluid loss, as well as other parameters. Various rheological evaluations using high-pressure, high-temperature rheometers as well as a foam loop, fluid leakoff testing, proppant pack conductivity, and regain permeability evaluations are presented. Field case histories will evaluate fracturing treatments using new fracturing fluid and comparable treatments using conventional fluid. Normalized production data of the treated wells of both systems are also compared.

A New Compositional Model for Hydraulic Fracturing With Energized Fluids

Summary Traditional fracturing models regard fracturing fluids as a single-component, single-phase fluid. This assumption is clearly incorrect for energized fluids where phase changes and mass transfer between phases play important roles in controlling fluid rheology, leakoff, and fracture geometry. A model is developed to simulate hydraulic fracturing with energized fluids. Compositional balances allow tracking of the changes in phase behavior and fluid properties, such as rheology and multiphase leakoff. An energy balance is implemented in order to consider temperature changes during fracturing. Phase behavior has been taken into account through an equation-of-state (EOS) formulation. These compositional- and phase-behavior effects are coupled with a geomechanical model for fracture propagation. It is shown that phase behavior and leakoff can change the composition and fluid rheology in the fracture significantly. This has a dramatic effect on the fracture geometry. Phase-behavior changes are coupled closely to the temperature and pressure changes in the fracture. The temperature, phase behavior, and partitioning of components in the liquid and gas phases have a significant effect on fracture dimensions. For example, shorter and wider fractures can be obtained by foaming an energized fluid. With the model presented, these temperature, pressure, and composition changes can now be modeled accurately and incorporated into the fracture growth and geometry.

Image Processing Techniques in Foam Characterization

Foam is one of the most widely used energized fluids in petroleum industry at fracturing and drilling operations. The influence of bubble size and texture on foam rheology has been observed for years. However, no mathematical description has been introduced yet. This study aims to consider the effects of bubble size and texture in determining the rheological parameters. Rheological analysis using digital image processing techniques and conventional methods are compared using information acquired from a developed set-up. It has been observed that by using digital image processing techniques, the rheological parameters of foam could be determined accurately.

Effect of ground and ceiling planes on shape of energized wakes

Energized wakes expelled by devices like thrust augmentors, propellers and rotors are studied theoretically in order to explore how their shape changes as they interact with ground and ceiling planes. It is found that when the airstream is stationary and the vehicle in hover, the presence of a ceiling plane causes an energized wake to constrict even more than when in an unbounded medium. The presence of a ground plane is found to cause the wake to constrict less than in free space. The computations also show that the vortex sheets first move inward before moving downward. Along their trajectory, the vortex sheets that separate the energized fluid from the ambient fluid have a nearly constant strength and velocity which indicates that the velocity just inside the wake is approximately constant. When a velocity is given to the wind tunnel airstream, the forward edge of the wake first rises and then descends so that it spends more time in the vicinity of the actuator disk. Implications of these results on measurements obtained in wind tunnels are discussed.